Will we be the last generation to see the Arctic with ice floes in summer?
As alarming as it is, the question now arises seriously since the planet may have crossed a tipping point towards irreversible global warming, some scientists believe.
Among them, the climatologist Markus Rex, responsible for the largest scientific expedition ever to the North Pole.
For nearly a year, his teams collected exhaustive data, during the months when their ship drifted in the Arctic ice.
The conclusions leave little room for optimism.
“The disappearance of summer ice in the Arctic is one of the first mines in the minefield, one of the tipping points we first trigger when we push warming too far,” he said. he explained at a press conference.
However, "one can really wonder if we have not already walked on this mine and triggered the start of the explosion", insisted the physicist.
Little known to the general public, these
can be compared to “climatic dominoes”, which lead to a cascade of repercussions on the ecosystem. “We see it, for example, with the bleaching of corals caused by greenhouse gas emissions. The degradation of the reef in turn leads to an impoverishment of marine life (decline in the number of fish, deterioration of algae and micro-organisms) ”, explains Clara Marino, PhD student in ecology.
Above all, the tipping point translates into an idea of irreversible rupture from one stage to another.
“It's as if we were climbing a step without it being ever possible to return to the one below”, summarizes the researcher.
An idea already widely evoked by collapsology, a current of thought which envisages the possible collapse of our civilization in particular because of global warming and the extinction of species.
The tipping points.
The melting of the ice caps, the thawing of permafrost, the disappearance of coral reefs or the decline of the Amazon rainforest are all “tipping points” identified by scientists as elements whose substantial modification could lead to dramatic climate change and irremediable. It should also be noted that these phenomena sometimes maintain themselves, as in the context of the melting sea ice, specifies Hervé Le Treut, climatologist member of the Academy of Sciences. “Ice helps protect the oceans. As this continues to melt, the ocean warms. Then the heat stored in the seabed ultimately prevents the ice from cooling. The question now is to know how far this vicious circle will end… ”, breathes the scientist.
A switch that does not happen in "a snap of the fingers"
While everyone agrees on the severity of the observed climatic phenomena, the semantics used to express them continue to divide the scientific world.
The notion of "tipping point" or "breaking point", introduced 20 years ago by the Intergovernmental Panel on Climate Change (IPCC), could even lead to some misunderstanding, according to Clara Marino.
“The phrase suggests that these changes are immediate, when it is a long process and not a snap of the fingers!
A reservation also shared by her colleague, Françoise Vimeux, climatologist at the Institute for Research for Development (IRD), preferring the notion of "threshold effect".
suggests that we are going to fall into a catastrophic, monstrous climate. In truth, we are mostly falling into a system that we are less familiar with, ”she adds. Likewise, the irreversible nature of such a concept must be put into perspective, says the researcher. “Faced with warming, the components of the climate system (atmosphere, oceans, land ice) have very different response times. It may take hundreds of years for an ice cap to reform. Certain changes will therefore be irreversible on the scale of a human life… but not in absolute terms, ”remarks Françoise Vimeux.
Finally, the fatality induced through this “breaking point” cannot really stick to reality, say the researchers. “It's not all a matter of no return, as the expression would have us believe. We still have the hand to change the average temperature of the Earth by the end of the 21st century, ”recalls, optimist, Françoise Vimeux. Thus, the IPCC report of 2019 ensures that limiting global warming to 1.5 ºC remains possible, on condition of “achieving unprecedented transitions at all levels of society”. It remains to be seen whether the means employed over the next few years will be commensurate with the urgency. Otherwise, new tipping points could multiply.